1. Field of the Invention
This invention relates to an inverse timer for utilization in process line so as to accommodate for the inertial time lag, i.e., the time of response of an instrument to be activated.
2. Description of the Prior Art
In a high speed processing line it is of pedestrian occurrence to take cognizance of processing instrumentation which has a time lag (inertial) response, and preactivate the instrument in anticipation of the arrival of the material to be processed. The time required for the material to travel from some point of detection to the instrument is determined; this is commonly referred to as the transport time. The reaction time of the instrument is either known from the manufacturer's specifications or it is determined empirically. The solution then is to activate the instrument .DELTA.T seconds after detection, where .DELTA.T is the difference between the transport time and the reaction time.
The prior art has solved this classic problem using an operational amplifier-integrator arrangement in which there is one potentiometer at the input end which nominally adjusts for the transport time delay, and one potentiometer in the feedback path of the integrator which nominally adjusts for the reaction time. (A third potentiometer independently adjusts for the distance from the point of detection to the instrument to be activated.)
The word nominally is here used advisedly because adjustment of the transport time potentiometer affects the reaction time setting, and conversely, adjustment of the reaction time potentiometer affects the transport time. These two potentiometers must therefore be laboriously adjusted one at a time in the field until the optimum result is empirically and sometimes (in the case of the less experienced operatives) fortuitously obtained.